Prior art anti-rotation systems are described, for example, in the patent publications JP2002-54708 and JP59-19762 and use anti-rotation structures forming part of the actuator or rigidly connected to it.
The traditional anti-rotation systems have the following limitations:                they are highly susceptible to misalignment between the actuator and the structure where the anti-rotation is performed; in particular, in all those applications with high operational loads and continuous operating conditions, the misalignments between actuator and anti-rotation structure generate transversal loads on the actuator which can lead to a malfunction of the device, a rapid deterioration of its performance and, therefore, a low reliability of the system;        all those applications with high operational loads and continuous operating conditions require large spaces for containing an anti-rotation structure which is sufficiently robust to satisfy the load capacity and duration requirements needed by the application;        they lead to an increase in the translatory masses of the actuator and, therefore, to a reduction in the dynamic performance of the system;        the anti-rotation systems of the sliding type are traditionally used where the pressures between the contact elements and the duration requirements are substantially reduced; in applications with high operational loads and continuous operating conditions, the sliding type anti-rotations systems can lead to a rapid deterioration of the performance and, therefore, to a low reliability of the system.        the anti-rotations systems are normally positioned in series relative to the recirculating ball screw element leading to a large axial dimension and, in any case, to the sum in series of the stroke of the screw with the stroke of the anti-rotation.        